1. Field of the Invention:
This invention relates to an image forming apparatus. More particularly, this invention relates to a reader printer which automatically discriminates between a negative film and a positive film, whichever has been put to use therein, and reproduces a positive image from the film in use on a recording paper.
2. Description of the Prior Art:
An image recording apparatus or a reader printer installed as in a library is more often than not charged indiscriminately with negative films and positive films. As concerns the discrimination of films by their kind, it is a common practice for an operator of the reader printer to use a given film to obtain a positive image from a negative film or a positive image from a positive film after he has judged whether the given film is a negative film or a positive film. The judgment of this nature is not necessarily easy when the operator is not accustomed thereto. There is the possibility of the operator committing an error in judging the kind of film and consequently miscopying the film by proceeding to reproduce an image of the film. In case where one operator of the reader printer produces a copy from negative film and a next operator of the same reader printer produces a copy from a positive film, if the latter operator forgets to set the kind of film, he is certain to miscopy his film because of wrong mode of image formation. In the circumstances, reader printers capable of automatically discriminating between positive films and negative films and copying a given film correctly have been longed for and proposed.
In the conventional reader printers vested with a function to effect automatic discrimination between negative films and positive films, that which is disclosed in Japanese Patent Publication 63-10,410 has been renowned. The reader printer taught by this patent publication is provided with a mode changeover switch for switching between the N-P mode for reproducing the image of a negative film as a positively copied image and the P-P mode for reproducing the image of a positive film as a positively copied image and a photoelectric transducer for admitting a light traveling through a given film and emitting a voltage signal in response to the incident light. By the output signal from the photoelectric transducer, this reader printer judges whether the original image is recorded in a negative film or a positive film. The mode changeover switch is automatically actuated in accordance with the signal from the photoelectric transducer. When a given film is judged as not discriminable, the mode changeover switch is allowed to be manually switched.
Since the films given to be handled for copying are widely varied in kind, such conventional reader printers as described above have the possibility of committing an error in effecting automatic discrimination of films by kind. Further, they have not been capable of displaying to their operators the kind of film found by automatic discrimination and the image forming mode used. When the operator is required manually to set again the mode proper to the kind of film, therefore, he is compelled to take a look at the film and draw the judgment personally.
In case where the mode is to be manually set again based on the discrimination between a negative film and a positive film, there is the possibility of the operator erroneously setting the mode once again. In this case, the production of a desired copy may possibly entail occurrence of two miscopied sheets. Thus, the conventional reader printers have suffered from very poor efficiency and conspicuous inconvenience of operation.